Loop corrections and a new test of inflation

TL;DR

This paper proposes a novel observational test linking the bispectrum and trispectrum to determine if single or multiple scalar fields generated primordial perturbations during inflation, with robustness against loop corrections.

Contribution

It introduces a new, loop-correction protected relation between the bispectrum and trispectrum to distinguish single-field from multi-field inflation models.

Findings

The test is theoretically robust against all orders of loop corrections.

It provides a new method to analyze the nature of fields during inflation.

The relation can help interpret future cosmological observations.

Abstract

Inflation is the leading paradigm for explaining the origin of primordial density perturbations and the observed temperature fluctuations of the cosmic microwave background. However many open questions remain, in particular whether one or more scalar fields were present during inflation and how they contributed to the primordial density perturbation. We propose a new observational test of whether multiple fields, or only one (not necessarily the inflaton) generated the perturbations. We show that our test, relating the bispectrum and trispectrum, is protected against loop corrections at all orders, unlike previous relations.